1. Field of the Invention
This invention relates to electrospinning. More specifically, the invention is a method of predicting as well as optimizing various parameters for an electrospinning system using a single exemplary test run of the system.
2. Description of the Related Art
Electrospinning is a polymer manufacturing process that has been revived over the past decade in order to produce micro and nano-fibers as well as resulting fiber groups (or mats as they are known) with properties that can be tailored to specific applications by controlling fiber diameter and mat porosity. The individual fibers are formed by applying a high electrostatic field to a polymer solution that carries a charge sufficient to attract the solution to a grounded source. The polymer solution is ejected as a stream from a spinneret. The stream is directed towards a collector where it forms a fiber thereon. Parameters that determine fiber formation include physical system parameters defining the spinneret, the collector, and the distance between the spinneret and collector, as well as material parameters such as polymer solution viscosity, polymer/solvent interaction, surface tension, applied voltage, and the conductivity of the solution.
Typically, only non-woven mats can be produced during this process due to splaying of the fibers and jet instability of the polymer expelled from the spinneret. These non-woven mats are used as scaffolds for tissue engineering, wound dressings, clothing, filters and membranes. While non-woven mats have proven to be useful for a variety of applications, controlling fiber alignment in the mat is a desirable characteristic to expand the applications of electrospun materials. Particularly for the case of tissue engineering scaffolds, the control of fiber distribution, fiber alignment, and porosity of the scaffold are crucial for the success of any scaffold. Current manufacturing techniques are limited by erratic polymer whipping that often produces dense nano-fiber mats, which cannot support cell infiltration or cell alignment.
An improved system for aligning fibers in an electrospinning process was recently disclosed in U.S. patent application Ser. No. 12/131,420, filed Jun. 2, 2008. Briefly, this new system and technique direct a jet of a fiberizable material towards an uncharged collector from a dispensing location that is spaced apart from the collector. While the fiberizable material is directed towards the collector, an elliptical (the term “elliptical” including elliptical and all dipole field-like shapes, including both symmetric and unsymmetric, and including both spherical and ovoid) electric field is generated. The electric field spans between the dispensing location and a control location that is within line-of-sight of the dispensing location such that the electric field impinges upon at least a portion of the collector. The generation of the elliptical electric field and placement of the uncharged collector therein provide for fiber alignment when the fiberizable material is deposited on the collector. However, development of a particular fiber mat design requires a lengthy trial-and-error process to establish the various system parameters.